A wind turbine can include a turbine that has a rotor that includes a rotatable hub assembly having one or more blades. The blades transform wind energy into a mechanical rotational torque that drives one or more generators via the rotor. The generators are sometimes, but not always, rotationally coupled to the rotor through a gearbox. The gearbox steps up the inherently low rotational speed of the rotor for the generator to efficiently convert the rotational mechanical energy to electrical energy, which is fed into a utility grid via at least one electrical connection. Gearless direct drive wind turbines also exist. The rotor, generator, gearbox and other components are typically mounted within a housing, or nacelle, that is positioned on top of a base that may be a truss or tubular tower.
Some wind turbine configurations include double-fed induction generators (DFIGs). Such configurations may also include power converters that are used to convert a frequency of generated electric power to a frequency substantially similar to a utility grid frequency (e.g., 50 Hz, 60 Hz, etc.). Moreover, such converters, in conjunction with the DFIG, also transmit electric power between the utility grid and the generator as well as transmit generator excitation power to a wound generator rotor from one of the connections to the electric utility grid connection.
In some implementations, the power converter can be a two-stage power converter that includes a rotor side converter coupled to the rotor of the DFIG and a line side converter coupled to the rotor side converter via a DC bus. The rotor side converter can convert AC power generated at the DFIG to DC power for the DC bus. The line side converter can convert DC power from the DC bus to AC power for application to, for instance, an electrical grid.
In some cases, a wind turbine may be controlled to provide output reactive power (e.g., VARS) to meet certain power demands or other functionality. To achieve the desired output reactive power, reactive current can be shifted from the stator of the DFIG to the line side converter. For instance, the reactive current can go to the rotor side converter which then spills over to the line side converter or between other components of a power system. Various gains can be used in the control logic for determining control commands for the output reactive current of the line side converter. In previous implementations, certain gains were static values. These static values may not allow for full spillover or shifting of the reactive current to the line converter.